Research On Embedded Clock Synchronization Technology And Security Analysis Based On BeiDou System

The Bei Dou system can provide high-precision timing services for global users,up to 10 nanoseconds.The pulse per second output by the Bei Dou receiver has the characteristics of high precision and good stability as well as sending the coordinated universal time information via a serial communication interface.However,the accuracy of clock synchronization is also affected by other factors such as synchronization algorithms and the stability of the hardware clocks in the devices.Because the civil signals of Bei Dou are public,Bei Dou receivers may be susceptible to deception and interference.In order to investigate these issues,this thesis builds a series of experimental platforms to analyze the clock synchronization methods based on PPS signals,and then explores the influence of Bei Dou signals spoofing interference on receiver timing.Firstly,this thesis introduces the principles of Bei Dou system’s time service to ground equipment through satellites,and analyzes the factors that affect the timing accuracy.Secondly,the principle of clock calibration using PPS signals are summarized as well as a clock synchronization method based on the Linux PPS driver and timing information output by the serial port of a Bei Dou receiver is designed.Then,different experimental platforms based on Raspberry Pi,a external hardware clock source and a Bei Dou receiver are built to explore the performance of clock synchronization methods such as the Linux PPS driver,NTP daemon(NTPd)and Chrony when using PPS signals.The experimental results show that when the original Raspberry Pi clock source is used,the performance of the three methods has a large decline with the increase of the synchronization interval,but after changing to a more stable clock source,the performance of these methods has been significantly improved.Finally,this thesis studies the structure of the Bei Dou satellite signal,analyzes the characteristics of satellite signal spoofing and interference,and designs the simulation algorithm of the Bei Dou B1 I signal according to the principle of forwarding deception.The spoofing signal transmitted by the software-defined radio equipment has interfered with the Bei Dou receiver’s time information such as day,month and year.